Neurons and glia in the developing cortex are derived from a pluripotent, neuroepithelial (NE) progenitor cells. My colleagues and I have shown that ciliary neurotrophic factor (CNTF) and platelet-derived growth factor (PDGF) direct cortical NE cells towards alternate fates. CNTF initiates formation of astrocytes while PDGF is a cure for neuronal development. The intracellular cues towards astrocyte or neuron formation are channeled through induction of actor-specific "immediate early" gene. The research described here builds upon these preliminary observations. I have three broad objectives. The first objective is to identify, clone and characterize "immediate early" genes that are up-regulated by CNTF and PDGF in cortical NE cells. An "undirected screen" will be conducted by differential colony hybridization of 1 phage cDNA libraries directed to CNTF or PDGF-treated NE cells. While the undirected screen is in progress, we will conduct a "directed screen" HLF transcription factor that are up-regulated by CNTF or PDGF. HLH transcription factors are salient components of the immediately early gene sets in other cells and tissues. Functional homologues of Drosophila HLH transcription factors have been shown to regulate neurogenesis in the rat peripheral nervous system. The second objective is to identify those immediately early cDNAs that encode intracellular mediators of astrocyte or neuron formation. This will be done by expressing CNTF/PDGF-responsive cDNAs in NE cells and monitoring for acquisition of an astrocytic or neuronal phenotype. In selecting cDNAs for functional analysis, we will rely on sequence data. We will focus on cDNAs that are factor-specific and correspond to low abundance mRNAs. Immediate early cDNAs that encode HLF-type transcription factors will receive highest priority for functional assays. The third objective is to screen for immediate early genes that are differentially expressed in primitive neural ectodermal tumors (PNETs) for children. These pediatric PNETs can be conceptualized as multipotent NE cells that are developmentally stalled. In collaboration with Drs. Segal and Pomeroy we will isolate HLH transcription factors that are differentially regulated in normal cerebellum versus malignant medulloblastoma (a cerebellar PNET). We will use DNA "chip" technology to isolate prognostic indicators for "standard risk" versus "high risk" medulloblastoma.